Separation of oil and water mixtures (e.g., oil-water emulsions or other mixtures where oil is suspended or otherwise present in water) is of great importance across a wide range of technologies and industries. As highlighted by the 2010 Gulf oil spill and subsequent cleanup efforts, there is a need in the art for oil recovery and separation technologies that are fast, efficient, and environmentally friendly. There is a need for separation technologies that can separate water droplets from water-in-oil emulsions and that can separate oil from oil-in-water emulsions (e.g., to comply with government regulations regarding the amount of oil in water that is discharged back into the environment). The petroleum industry faces similar challenges as it attempts to extract oil from beneath the sea or simply to extract oil from oil-water emulsions.
Existing separation devices and methods are either environmentally unfriendly, extremely energy intensive, or incapable of performing the desired separations (or a combination of these). For example, in deep sea oil extraction, one energy-intensive conventional approach is to pump oil emulsified in water from the ocean floor to the surface where it is stored it in gravity separation tanks. In addition, once much of the water has been removed from the oil, existing techniques (e.g., ultracentrifugation) are incapable of removing additional, trace amounts of water that remain. These trace amounts of water in oil may cause significant problems for end users, process equipment, and machinery. In addition, conventional techniques are incapable of removing trace amounts of oil from water—and these trace amounts of oil in water can cause significant problems for end users. In addition, only water with oil levels below a predetermined threshold may be discharged into the environment after cleaning. Current separation techniques are therefore inefficient and/or incapable of performing the wide range of oil and water separations of interest.
In recent years, growing environmental concerns have fueled the need for efficient separation of oil-water mixtures. Oil spills, as highlighted by the Deepwater Horizon spills, have lasting detrimental ecological effects. The threat is recurring and persistent; every year over 20,000 oil spills are reported to the U.S. government. Aside from such disasters, fats, oils, and grease are classified as hazardous waste and their removal (e.g., from water before the water being released into the environment) is subject to increasingly more stringent governmental regulation. Generally, according to U.S. regulations, water needs to be cleaned to about 10 ppm of oil or less prior to being discharged.
There is a need for more efficient and more environmentally-friendly devices and methods for separating oil and water mixtures. In particular, a need exists for separating trace amounts of water from oil and water mixtures. In addition, a need exists for separating oil (including trace amounts of oil) from water without removing large quantities of water—e.g., there is a need for devices and methods capable of separating oil from water locally. Moreover, there is a need for devices and methods capable of separating oil from water to obtain water that does not include oil or includes only such an amount of oil as is acceptable to comply with government regulations for discharging water back into the environment. Oil-contaminated water is a serious environmental problem, and fast and efficient methods are needed to remove oil from water, e.g., after an oil spill.